1. Field of the Invention
This invention is concerned with a fibre-reinforced plastic (FRP) honeycomb sandwich structure in which a honeycomb core is arranged parallel to panel surface in order to solve the peel-off problem between hull and core in the prior art and is concerned with a honeycomb core assembly set tank in which a lot of FRP internal tanks are gathered into honeycomb core assembly.
2. Description of the Prior Art
As a social background, global warming and dryness of fossil resource are given. One answer with possibility to these large questions is a fuel cell power generation system. Everybody knows even if the highest technology of the modern civilization is made good use of, the fossil fuel that is the inheritance of earth resource cannot be reproduced. When we enjoy the modern civilization in every day living, it is inevitable and irreversible to consume the fossil fuel.
The fuel cell generates electric energy from “Hydrogen (H2)” and “Oxygen (O2)”, and the exhaust is “Water (H2O)”. In the power generation process, the fuel cell system does not exhaust the carbon dioxide assumed to be a cause of global warming. Present days, “Hydrogen (H2)” used for the fuel cell is refined from LNG which is the fossil fuel.
However, predecessors of the modern civilization left us the reproducing scientific theories for “Hydrogen (H2)” which is the fuel of the fuel cell. Even if the highest technology of the modern civilization is made good use of, the fossil fuel that is the earth resource cannot be reproduced. On the other hand, the power generation system of the fuel cell can be reproduced, even if it is now only the theory on the desk. Near future, the fuel cell has a possibility of being the energy system for our life to be an ideal energy system.
The fuel cell is an ideal energy system, indeed. However, it is necessary to overcome the two big difficulties for the practical use. One is a power generation cell of the fuel cell, and another one is a hydrogen tank. The power generation cell of the fuel cell has been improved by marketing now. However, the development of the hydrogen tank is still difficult.
Hydrogen is a gas at the normal temperature, and the liquefaction temperature in the atmospheric pressure is an extremely low temperature at degree of −200° C. or less. Moreover, the gas hydrogen of 4% is mixed with the oxygen in the air, and when the spark flies to neighborhood, it burns explosively. Handling is very difficult. Safety demands that the design and characteristics of the hydrogen tank be rated for world class performance. The hydrogen tank for the car has been researched in each car manufacturer, and the structural strength has achieved 750 atmospheric pressures now. However, there are some defects in the tank volume, shape and the spacing.
The difficult problem when we put the fuel cell to practical use in our life is transportation of hydrogen. As for hydrogen, if it is not liquefied, the transportation efficiency is too inferior to liquid gasoline because molecular weight is very small. However, the liquid hydrogen is not obtained if it does not cool to the extremely low temperature of −200° C. or less. It costs much to transport the liquid hydrogen with the vehicle only for special use.
Additionally, the difficult one is a hydrogen station. A similar hydrogen station to the gas station is necessary for the spread of the fuel cell powered vehicle. The internal pressure of the hydrogen tank in a state-of-the-art vehicle is 750 atmospheric pressures now. Therefore as for assumed hydrogen station, it is necessary to equip an underground tank with fully cooling system keeping the liquid hydrogen at minus 200° C. or less and also it is necessary to equip a pressurizing system which pressurizes the hydrogen gas to 750 atmospheric pressures. It is forecast that not only the installation cost but also maintenance cost becomes huge for the assumed hydrogen station.
Moreover, it is difficult to confine the liquid hydrogen in an underground tank of the normal temperature when the cooling function is lost by any chance. As a result, the situation in which most of the liquid hydrogen preserved at the hydrogen station should be discharged in air is thought, too. Because the gas hydrogen is an explosiveness gas, it is large issue for safety.
These are the problems and the current state that are demanded of the storing system for hydrogen gas. The fuel cell power generation system has the possibility of becoming the energy system that can be called ideal. However, the achievement of ideal energy system demands to us the research and development of cooperation and endurance.
The honeycomb structure has a good deal of benefits in lightweight and rigidity, thus the honeycomb sandwich panel has been widely adopted as a structure material in the architectural field and the aircraft field.
However, in a usual prior art the honeycomb core, a set of a lot of honeycomb cells, is manufactured from cardboard, mold plastic and lamina aluminum. Their structural strength are insufficient to support the vertical load on side surface, so, the honeycomb core cannot be arranged parallel to the surface in the honeycomb sandwich panel. In the prior art the direction of honeycomb core is arranged vertical to the panel surface, thus the hull is bonded on a small area of the six-corner edges of honeycomb core assembly. In a usual prior art, honeycomb sandwich panel cannot avoid the peel-off problem between the honeycomb core and hull. The peel-off problem is the fatal defect of the honeycomb sandwich panel.
The patent No. 4862975 in Japan, a manufacturing method of honeycomb core made from FRP prepreg is indicated. And it shows the manufacturing process in which the honeycomb core assembly is arranged parallel to the surface of honeycomb sandwich panel.
However, the manufacturing process of patent No. 4862975 is very complex and is inferior to productivity. And the shapes of six-corner honeycomb cells are easily distorted.